A thermoplastic resin is a useful industrial material being used for a molded plastic article, film, fiber, adhesion, paint, an extruded sheet and the like. Generally such a thermoplastic resin is superior in light weight, impact resistance, abrasion resistance, electrical insulating property and moldability. Further, there is a transparent thermoplastic resin. However, such a thermoplastic resin has weak points in that the mechanical strength, heat resistance and weather resistance are not enough and its flammability is high and further it produces a harmful gas in combustion.
In recent years, in addition to a current general-purpose plastics, engineering plastics, which have high strength and rigidity and high heat resistance to 100.degree. C. or more, have been developed and have been widely used as industrial materials replacing metal. Generally, the high heat resistance of these engineering plastics is realized by the fact that they have a rigid structure originating from a main chain of phenylene groups; however, they have a problem in that the moldability, which is a characteristic of a plastic, has been lost.
Since thermoplastic resins, except polyvinyl chloride and some engineering plastics, are easy to burn, it is generally made fire-retardant by adding a fire retardant, typically a halogen compound, when fire-retardance is required. However, there are problems in a halogen fire retardants, such as that it produces a more harmful gas than the thermoplastic resin itself when it is combusted and it sometimes occurs that the mechanical strength may decrease dependent on the amount of it added.
As a means to improve moldability and fire-retardance of a thermoplastic resin, a method in which a siloxane compound is added to a thermoplastic resin has been proposed. However, when the compatibility between a siloxane compound and a thermoplastic resin is low in this method, there are problems that moldability and fire-retardance may not be sufficient or the siloxane compound may bleed on the surface of a molded products of a thermoplastic resin.
As means to solve the above-mentioned problems, a technology based on siloxane copolymers has been proposed. For example, in Japanese Laid-Open Publication No. 5-262975, fire retardant polycarbonate-siloxane block copolymer has been proposed. In Japanese Laid-Open Publication No. 5-222173 and Japanese Laid-Open Publication No. 7-2999, polyester (polyester carbonate)-siloxane block copolymer has been proposed. Furthermore, in Japanese Laid-Open Publication No. 5-155999, polycarbonate having polysiloxane as a side chain has been proposed. However, it is inevitable in these siloxane copolymers that the mechanical strength decreases due to a phase separation when the introduced amount of siloxane units increases, because the siloxane units may form a block. Therefore there is a limit to the amount of siloxane units introduced, and there may be the problems that sufficient fire retardance and moldability are not obtained.
As a means to solve problems of the siloxane block copolymer, a technology based on a siloxane alternating copolymer has been proposed. For example, Curry et al. has reported a synthetic method for a siloxane copolymer obtained from a diol and bis(anilino)diphenylsilane (J. Appl. Polym. Sci., vol. 9, pp. 295 (1965)). Carraher, Jr. et al. has reported a synthetic method of a siloxane copolymer obtained from diol and dichlorodiorganosilane (J. Polym. Sci., part A-1, vol. 8, pp. 973 (1970)). In these methods, it becomes possible to increase the introduced amount of siloxane because a polymer produced becomes an alternating copolymer. However, since an expensive specific silicon compound is used in these methods, the production cost becomes high and further there is a problem that it takes a long time for the reaction.
The present invention has been developed in order to solve the above-mentioned problems, and its purpose is to overcome the usual weak points of the above-mentioned siloxane copolymer and to offer a siloxane random copolymer which is superior in fire retardance, transparency, moldability, mold releasing property and surface lubricating property, and a resin composition containing the same. The subject of the invention overcomes a weak point of a producing process of the above-mentioned usual siloxane copolymer and offers a process by which these copolymers can be produced simply, easily and is economically on a commercial basis.
The present inventors have made many studies and have found that a siloxane random copolymer, which has a specific structural unit, can solve the above-mentioned problems, and have completed this invention.